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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="foreach.portability"></a><a class="link" href="portability.html" title="Portability">Portability</a>
</h2></div></div></div>
<p>
      <code class="literal">BOOST_FOREACH</code> uses some fairly sophisticated techniques
      that not all compilers support. Depending on how compliant your compiler is,
      you may not be able to use <code class="literal">BOOST_FOREACH</code> in some scenarios.
      Since <code class="literal">BOOST_FOREACH</code> uses <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>,
      it inherits <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>'s
      portability issues. You can read about those issues in the <a href="../../../libs/range/doc/html/range/portability.html" target="_top">Boost.Range
      Portability</a> section.
    </p>
<p>
      In addition to the demands placed on the compiler by <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>,
      <code class="literal">BOOST_FOREACH</code> places additional demands in order to handle
      rvalue sequences properly. (Recall that an rvalue is an unnamed object, so
      an example of an rvalue sequence would be a function that returns a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;&gt;</span></code> by value.) Compilers vary in their
      handling of rvalues and lvalues. To cope with the situation <code class="literal">BOOST_FOREACH</code>
      defines three levels of compliance, described below:
    </p>
<div class="table">
<a name="foreach.portability.t0"></a><p class="title"><b>Table&#160;9.1.&#160;BOOST_FOREACH Compliance Levels</b></p>
<div class="table-contents"><table class="table" summary="BOOST_FOREACH Compliance Levels">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
              <p>
                Level
              </p>
            </th>
<th>
              <p>
                Meaning
              </p>
            </th>
</tr></thead>
<tbody>
<tr>
<td>
              <p>
                <span class="bold"><strong>Level 0</strong></span>
              </p>
            </td>
<td>
              <p>
                <span class="emphasis"><em><span class="underline">Highest level of compliance</span></em></span><br>
                <code class="literal">BOOST_FOREACH</code> works with lvalues, rvalues and
                const-qualified rvalues.
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                <span class="bold"><strong>Level 1</strong></span>
              </p>
            </td>
<td>
              <p>
                <span class="emphasis"><em><span class="underline">Moderate level of compliance</span></em></span><br>
                <code class="literal">BOOST_FOREACH</code> works with lvalues and plain rvalues,
                but not const-qualified rvalues.<br> <code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_CONST_RVALUE_DETECTION</span></code>
                is defined in this case.
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                <span class="bold"><strong>Level 2</strong></span>
              </p>
            </td>
<td>
              <p>
                <span class="emphasis"><em><span class="underline">Lowest level of compliance</span></em></span><br>
                <code class="literal">BOOST_FOREACH</code> works with lvalues only, not rvalues.<br>
                <code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_RVALUE_DETECTION</span></code>
                is defined in this case.
              </p>
            </td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p>
      Below are the compilers with which <code class="literal">BOOST_FOREACH</code> has been
      tested, and the compliance level <code class="literal">BOOST_FOREACH</code> provides
      for them.
    </p>
<div class="table">
<a name="foreach.portability.t1"></a><p class="title"><b>Table&#160;9.2.&#160;Compiler Compliance Level</b></p>
<div class="table-contents"><table class="table" summary="Compiler Compliance Level">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
              <p>
                Compiler
              </p>
            </th>
<th>
              <p>
                Compliance Level
              </p>
            </th>
</tr></thead>
<tbody>
<tr>
<td>
              <p>
                Visual C++ 8.0
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Visual C++ 7.1
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Visual C++ 7.0
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Visual C++ 6.0
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                gcc 4.0
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                gcc 3.4
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                gcc 3.3
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                mingw 3.4
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Intel for Linux 9.0
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Intel for Windows 9.0
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Intel for Windows 8.0
              </p>
            </td>
<td>
              <p>
                Level 1
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Intel for Windows 7.0
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Comeau 4.3.3
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Borland 5.6.4
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Metrowerks 9.5
              </p>
            </td>
<td>
              <p>
                Level 1
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                Metrowerks 9.4
              </p>
            </td>
<td>
              <p>
                Level 1
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                SunPro 5.8
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                qcc 3.3
              </p>
            </td>
<td>
              <p>
                Level 0
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                tru64cxx 65
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                tru64cxx 71
              </p>
            </td>
<td>
              <p>
                Level 2
              </p>
            </td>
</tr>
</tbody>
</table></div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2004 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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